The present invention is a sample splitting device used to divide a larger sample of particulate material into representative smaller samples.
One of the most difficult problems in obtaining accurate analyses of granular or particulate materials resides in representative sampling of the product. Many products, such as ores, are sold on the basis of the amount of contained mineral materials. The price of other products, such as wood chips sold to pulp mills, is based on the dry weight of material contained within a naturally wet product. If pulp chips may be taken as an example, obtaining representative samples is extremely difficult because of the non-uniformity within the product itself. There is usually great variation in moisture content from point to point within a given shipment. The usual strategy used to deal with this problem is to take frequent samples. However, this frequently exceeds the ability of shippers or buyers to test the materials. It is, therefore, customary to blend an initial set of samples and remove a representative sub-sample for testing.
A good sample splitter should meet all of the following criteria: (1) the sub-sample must be representative: (2) the splitter should be easy and simple to use; (3) it should be easy to maintain and preferably have no electrically driven components so that it can be used at remote locations; (4) it should yield a consistently sized test sample in a single pass through the device, even when the initial samples vary substantially in size; (5) it should not lose any fine particles nor have any tendency to be plugged or bridged over by the larger ones.
There are a variety of sample dividing or splitting devices commercially available. None of these, until the time of the present invention, have been able to meet all of the above criteria.
Sample splitters have assumed a wide variety of forms. This variation may be readily seen by consulting the patent and technical literature in the field. One method of sample splitting involves pouring the material over a cone or pyramid. Fins or baffles associated with the cone then direct the sub-samples into bins. This method has a major deficiency due to difficulty in uniformly centering the sample over the cone when it is poured into the splitter. Considerable bias can be introduced when the sample is not accurately poured from a point directly above the projected axis of the cone. The most minor departure from uniform centering prior to the sample striking and passing the splitter cone will introduce inaccuracy. When samples are poured by hand it is almost impossible to avoid too much of the sample hitting one side of the cone.
The following U.S. patents are exemplary of attempts to overcome the above problem: Pizzirani et al, U.S. Pat. No. 2,379,921; Herrold, U.S. Pat. No. 2,405,951; Haskell et al, U.S. Pat. No. 2,848,144 and Rathnow et al, U.S. Pat. No. 3,942,338.
While the above sampling devices may be useful for the purpose intended, they all tend to be quite complex and are expensive or difficult to use. The present invention has fully overcome the above problems.